Fiber optics scan system



BSD-96.25

June 1968 K. w. HARPER FIBER OPTICS SCAN SYSTEM 2 Sheets-Sheet 1Original Filed March 25, 1964 frv l/en tor: lfennar'd W Harper;

His 2'' terns June 25, 1968 K. w. HARPER 3,389,950

' FIBER OPTICS SCAN SYSTEM Original Filed March 25, 1964 2 Sheets-Sheet2 122 a H f In vent'or': Hennar'd W Harper;

HA: ttorney.

United States Patent 3,389,950 FIBER OPTICS SCAN SYSTEM Kennard W.I-Iarper, Ithaca, N.Y., assignor to General Electric Company, acorporation of New York Continuation of application Ser. No. 354,638,Mar. 25, 1964. This application Oct. 18, 1967, Ser. No. 677,001 6Claims. (Cl. 350-96) ABSTRACT OF THE DISCLOSURE The subject inventionrelates to an improved optical scanning system, and more particularly,to a scanning system utilizing fiber optical elements. In a preferredform, the system comprises three fiber Optics components: a centralspherical element, a second element having a concave surface mating withthe spherical element for focusing an image thereon, and the third fiberoptic element also having a concave surface mating with said sphericalelement for deriving an image therefrom. A liquid may be providedbetween the mating surfaces which has a refractive index similar to thatof the fiber optics. Additional means are provided for supporting thethree fiber optic elements in position and for maintaining the centralspherical member at half the angular displacement of the first opticselement during scanning. Using a spherical central element, it ispossible to conveniently provide for scanning about two orthogonal axes.

This is a continuation of application Ser. No. 354,638, filed Mar. 25,1964, now abandoned.

It is frequently necessary for optical systems to scan through aconsiderable angle for detection and observation purposes. The scanningis usually accomplished by scanning or rotating the complete opticalsystem oralternatively through use of an array of optical prisms whichswing through the required angle. The principal problem encountered inswinging the complete optical system is the space required, particularlysince the complete system often includes sensors such as infrared ortelevision camera tubes. The use of rotating prisms also providesproblems in that the rotation of a prism also rotates the image, whichin turn requires a correction by a derotation prism and its associatedassorted correcting lenses. The speed of the optics of the system alsoprovides limitations on the selection of a scanning system. In a prismsystem the speed of the optical system is limited due to the largediameter lens system required back of the objective system to collectthe edge rays. This means that the energy collecting capabilities of theprism system are limited to around f/2 to j/3. Typical applications foroptical systems which operate, for example, in the infrared regionnormally require relatively fast optics of around f/1.0 while at thesame time providing only l a minimum of space available for the optics,precluding the rotation of the complete optical system which usuallyincludes a camera tube or infrared vidieon.

It is an object of the subject invention to provide an improved wideangle scanning system requiring a minimum of space and moving partswhile providing optimized energy collecting capabilities.

It is another object of the subject invention to provide an uncomplexscanning system in which portions of the system need only traverse aportion of the angle scanned.

It is yet another object of the subject invention to provide anuncomplex and compact scanning system suitable for relatively rapidscanning.

It is still another object of the subject invention to provide a wideangle scanning system which minimizes "Ice the number of componentswhich need be moved to perform the scanning function.

It is a further object of the subject invention to provide an improvedscanning system requiring only a relative small envelope yet including arelatively large optical entrance pupil.

Still further objects and advantages of the invention will becomeapparent as the following description proceeds and the features ofnovelty which characterize the invention will be pointed out withparticularity in the claims annexed to and forming a part of thisspecification.

In accordance with one form of the invention, a fiber optics scan systemis provided which utilizes fiber optic bundle members comprising a firstrotatable fiber optics member having a substantially circular crosssection with means for rotating the member about its axis of curvature.A second fiber optics member has a mating portion of circular crosssection closely separated from the first member. Optical means areprovided to focus an image on the first member of circular cross sectionin a direction generally along the length of its optical fibers. Theoptical fibers of the coherent fiber optics members extend substantiallyparallel to a fiber extending axially to the circular section.

More particularly, the optical means includes a third fiber opticsmember having a substantially circular cross section portion closelymating with a portion of the first fiber optics member different fromthat mating with the second member. A liquid is provided between themating surfaces which has a refractive index similar to that of thefiber optics members. The first optical member is driven at a fraction(one-half) of the angular speed through which the optical means arerotated to perform a scanning function. The scanning angle viewed by thesecond fiber optics member through the first fiber optics member and theoptical means is twice the angle through which the first fiber opticsmember is rotated.

For a better understanding of this invention, reference may be had tothe accompanying drawings in which:

FIG. 1 is a diagrammatic showing of an optical system incorporating theinvention,

FIG. 2 is a diagrammatic showing of the system shown in FIG. 1illustrating certain optical relationships involved as the systemaccomplishes a scanning function.

FIG. 3 is a perspective view of a simplified showing of the mountingarrangement of the elements shown in FIGS. 1 and 2.

FIG. 4 is an alternate embodiment of the invention utilizing amultiplicity of certain of the elements in order to provide an opticalswitching arrangement for scan purposes; and

FIG. 5 is another embodiment of the invention utilizing the invention inan articulated arm optical system.

Referring to FIG. 1, there is shown an optical scan system incombination with a television camera pick-up tube 1 having a face plate2 and a tube aperture illustrated by the arrow 3. Contiguous to the faceplate 2 is a fiber optics lens system 4 comprising a fiber opticscollector lens 7, a fiber optics cylinder or ball or sphere 8 and afiber optics corrector lens 9.

Optical fibers are transparent fibers which transmit light alongselected paths and as in the instant invention may be formed in coherentbundles to transmit complete images free from any of the restrictioncharacteristics of conventional optical systems in a manner more fullydescribed, for example, in McGraw-Hill Encyclopedia of Science andTechnology," McGraw-Hill Book Co., Inc., 1960, under the topic beginningat page 348 entitled Optical Fibers and the bibliography cited therein.

The fiber optics corrector lens 9 is generally cylindrical having a baseor face 11 which may be planar to conform to the transparent face plate2 of the camera pickup tube 1 and an axially opposed concave matingsurface 12 having the same radius of curvature as the fiber opticssphere 8. Alternatively, the fiber optics corrector lens 9 can beprovided as the face plate of the pick-up tube 1, thus providing a dualfunction.

The fiber optics collector lens 7 is of generally cylindrical shapehaving a surface 15 which can be shaped to the Petzval curve (focusplane) of the lens system which is used to focus the incoming image onsurface 15. Axially opposed to surface 15 is a concaved mating surface16 having the same radius of curvaturme as the sphere 8.

The fiber optics collector lens 7, ball 8 and corrector lens 9 arefabricated of fiber bundles of suitable material for the type ofradiation involved. For use with visible light, 5-15 micron fibersaligned to form a coherent system and bonded or fuzed together bystandard techniques may be used. It has been found that micron fiberswith a numerical aperture of 0.66 as manufactured and sold by MosaicsFabrication of Southbridge, Mass, is suitable. The small fibers providebetter reslution. For use with infrared radiation, a fiber opticsmaterial of in the 1.5 to 6 micron region can be obtained through use ofAs S glass or other suitable material, drawn, clad, and put together incoherent bundles. The wavelength encountered in use is considered indeterming the material to be used. After the bundles of optical fibersare bonded to the size required, the desired optical curves are groundand polished. The fiber optics correction lens 9 and collector lens 7can, if desired, be shaped to magnify or minify as well as changing theviewing angle.

The clearance between the fiber optics ball 8 and the fiber opticscollector lens 7 and corrector lens 9 is kept small to approximately0.0005" and the opposed surfaces are wetted by 'a lubricant having arefractive index the same as or similar to the index of the fiberoptical material. It has been found that with the Mosaics Fabricationfiber optic material described above, a lubricant having a suitableviscosity and wetting power was found to be silicone XF-l060 sold by theGeneral Electric Company, thinned one part to two parts of silicone XF-1050. This lubricant enables the space between the contiguous faces ofthe fiber optic material to be kept to a minimum to avoid image spreadbetween adjacent fibers which can affect the resolution obtainable withthe system. The incoming radiations are focused on the fiber opticscollector lens 7 in the direction of the optical fibers thereof by thecollecting optical system lens which may, by way of example, be a 1 inchf/ 1.9 objective lens.

While the silicon lubricant described above has sufficient wetting powerto provide lubrication without immersing the mating portions of thefiber optics lens system 4 in a lubricating reservoir, the system can beprotected from dirt and other contaminants by surrounding the fiberoptics lens system with a housing and filling the housing with thelubricant.

As shown in FIG. 1, the fiber optics collector lens 7 is supported by asupport member having a radially extending flange 31 while the fiberoptics corrector lens 9 is similarly supported by a support member 32which also has a readily extended flange 33 portion. The fiber opticsball 8 is supported for rotation by a gimbal ring 35 fastenedcircumferentially around a great circle thereof and pivoted for rotationby gimbal pins (not shown) which extend in a direction perpendicular tothe intersection of the axis 22 and center line 23 that is perpendicularto the sheet of FIG. 1 at the center of the sphere 8. Rubber sleevemembers 37 extend between the central regions of the flanges 31 and 33of the support members 30 and 32, respectively, and may, if desired, bea single sleeve passing around the gimbal ring 35. Thus, a contatiner orreservoir is formed between the concave surfaces 12 and 16 of the fiberoptics lens 9 and 7 respectively which surrounds the fiber optics ball 8in the region where it mates with the fiber optics lens. This reservoiris filled with a silicone lubricant 28 or equal of the type describedabove.

The support member 30 of the fiber optics collector lens 7 is rigidlyconnected to the scanning collecting optical system lens 20 by agenerally conically shaped metallic member 39 forming the scanningoptics 40 which moves as a single member. A plurality of springs, suchas 41 and 42, extend between the circumference of the flange 31 of thesupport member 32 and the gimbal ring 35 while a plurality of additionalsprings extend between the gimbal ring 35 and the circumference offlange 33 of the support member 32. The scanning optics 40 is mountedfor rotation by a gimbal mounting described below in regard to FIG. 3 toenable rotation thereof independent of the rotation of the fiber opticsball 8. The axis of rotation of the scanning optics 40 lies along thesame axis as that for gimbal ring 35.

As shown in FIG. 1, the various portions of the optical system arealigned along the axis 22 of the camera pick-up tube 1. It is noted thatfor the direct line of sight shown in FIG. 1 the individual opticalfibers 24 of the fiber optics members 7, 8 and 9 which arediagrammatically shown by the parallel lines thereof lie parallel to theaxis 22. A light ray passing through the center of the scanning optics40 along axis 22 will pass through the sphere 8 along the fiber 26 lyingalong axis 22. FIG. 2 illustrates the scanning operation involved.

Referring to FIG. 2, it will be seen that the scanning optical systemlens 20 and the fiber optics collector lens 7 have been rotated throughan angle of 45, the fiber optics sphere 8 has been rotated through anangle of /2 of 22.5 from the axis of the camera pick-up tube 1 and thefiber optics corrector lens 9 and pick-up tube have remained stationary.The path of a light beam being received by the scanning optical systemlens 20 is successively through the fiber optics collector lens 7, fiber26 of ball 8, and fiber optics corrector lens 9 to the camera pick-uptube 1.

The two to one angular rotation ratio between the scanning optics 40 andthe fiber optics sphere 8 may be accomplished as follows: The varioussprings 41, 42, 43 and 44 have the same force per inch of deflection andare of equal length such that a simple mechanism is provided for drivingor rotating the fiber optics ball 8 at a half speed as compared with thecollecting lens 20 and 7. The springs can be either of the tension orcompression type. Moving the scanning optics 40 as shown in FIG. 2compresses the springs 42 and 44 causing the ball 8 to turn or rotate inthe direction of the compression. Since the opposing springs 41 and 43provide a balance, the ball keeps its motion centered to /2 the angle oftravel of the scanning optics 40. The sleeve members 37 when utilizedwith springs 4144 are selected to be light and flexible so as to impartpractically no force or motion on the ball.

It is possible with a lesser degree of accuracy to utilize the rubbersleeves not only as the sealing means but as the half speed proportionalcontrol if sleeves of proper resiliency are selected. However, ingeneral the angle through which such an arrangement will operate will beless than that for springs and, furthermore, it is more ditficult tobalance or adjust the precise relative movement of the movable members.However, because of its lower cost, where precision of motion is not aprime requirement, rubber sleeves having a heavier wall and properresiliency may be utilized in place of the springs.

It is possible to obtain a more direct control of the scanning operationwith considerable accuracy by driving the ball 8 and scanning optics 40by independent servo mechanism, servo mechanism drives, which for eachaxis of rotation of a gimbal mounted system and having the properproportional speed driving relationship therebetween.

While FIGS. 1 and 2 illustrate the rotation or scanning in a singledirection, the ball 8 and scanning optics 40 may be mounted in multiplegimbal mounting arrangements of the type utilized for gyroscopes toenable rotation in all directions to obtain a conical scan if desired.Additional pairs of springs would be utilized in that case and spacedcircumferentially around the gimbal ring of the ball 8. FIG. 3illustrates in a somewhat diagrammatic form a simple gimbal mountingarrangement to enable scanning in a plurality of directions.

Referring to FIG. 3, it is seen that the optical lens 20, member, andthe support member 30 which supports the fiber optics collector lens andwhich comprise the scanning optics are rotatably mounted via mountingpieces 51 and 52 which connect between the radial flanges 31 of thesupport member 30 and the pivots 54 and 55 on gimbal 57. FIG. 3 showsthe system in the position of FIG. 2 in that the scanning optics 40 isdepressed about the pivots 54 and 55, the axis of which passes throughthe center of sphere 8. Gimbal 57 is in turn itself supported by a pairof diametrically opposed pivots or axes 58 and 59 which lie on an axisperpendicular to the axis of pivots 54 and 55 and also passes throughthe center of sphere 8. The pivots 58 and 59 of gimbal 57 are supportedby support members 61 and 62, respectively, which in turn are mounted onbase member 64. Thus, vertical scan of scanning optics 40 is providedabout pivots 54 and 55 while horizontal scan is provided by the rotationof gimbal 57 about the pivots 58 and 59.

Similarly, the fiber optics sphere 8 is separately supported forrotation or scan in either the vertical or hori- Y zontal direction.Gimbal 63 is rotatively supported by a pair of pivots 65 and 66 whichare stationary relative to base 64. This vertical axis through pivots 65and 66 asses through the center of sphere 8 and enables rotation of thesphere which is supported thereby in a horizontal direction. Thevertical rotation of sphere 8 is made possible through the rotationabout the horizontal axis of the pivots 67 and 68 which connect betweenthe gimbal 57 and the gimbal 35 connected to the sphere 8.

Thus, the scanning optics 40 and the sphere 8 are mounted for rotationboth vertically and horizontally by their separate gimbal mountingarrangements which in combination enable a conical scanning operation.

It is possible for certain applications to omit the fiber opticscollector lens 7 and focus the incoming rays directly through thescanning optical system lens 20 to the fiber optics ball 8. However, theresolution and versatility of such an arrangement would not be as goodas that obtained through use of the fiber optics collector lens.

FIG. 4 illustrates an alternate embodiment of the scanning mechanismillustrated by FIGS. l-3 in which instead of utilizing a movable fiberoptics collector lens, a plurality of stationary radially'extendingfiber optics collector lenses or bundles may be selectively connected toa stationary output collector lens through the rotation of the fiberoptics ball or cylinder.

Referring to FIG. 4, there is illustrated in simplified form a fiberoptics optically switching light valve comprising a rotatably mountedfiber optics ball or cylinder 108, cooperating with a fiber opticscollector lens 109, which in turn is optically connected to a camerapick-up tube 101 in a manner similar to that of the device illustratedby FIGS. 1-3. However, instead of utilizing a rotatable fiber opticscollector lens such as 7 of FIG. 1, there are mounted a plurality ofcollector lenses or bundles 107a, 107b, and 1070 spaced for example,with their axes 122, respectively, aligned with and 10 to 15 degrees oneither side of the axis 122 of the camera pick-up tube 101. Thelubricant reservoir, gimbal mounting arrangement, drive, and otherdetails are not shown in the interests of brevity, but may be of thegeneral type shown in FIGS. 1-3.

The optical system of FIG. 4 through the rotation of the fiber opticsball 108 in a clockwise direction as indicated by arrow 110 willselectively switch the image received by the camera tube 101 via thefiber optics collector lens 109 from that viewed by the collector lens107b to that viewed by the collector lens 107a. The ball 108 will berotated through an angle 0/2 which is half the angle between the axis ofthe collector lens 107b and 1071:. Similarly, rotation of the fiberoptics ball 8 in a counter clockwise direction through an angle equal to0/2 can selectively switch the output received through the collectorlens 109 from that viewed by the collector lens 107b to that viewed bythe lens 107c. Thus, there is provided an optical switching arrangementor light valve which enables the selective scanning or optical switchingbetween preselected directions in the manner described in regard toFIGS. l-3. If it is not necessary to transmit a coherent image but onlyperform an optical switching function, only the fiber optics ball 108need be of coherent fibers.

It is sometimes desirable to provide a flexible line of sight in which acoherent image is to be transmitted over a distance where space is at apremium in various remote viewing devices. For example, it may bedesirable to transmit coherent optical images over distances and aroundcorners to cover a very wide angle of observation to enable a clearviewing of what is happening at the end of an articulate arm ormanipulator.

FIG. 5 shows a fiber optics pipe system going around two elbows orcorners which if gimbal mounted will provide two axes of freedom abouteach of these elbows.. As in FIG. 4. the figure is in simplified formwith the reservoir, mounting, drive, and other details omitted in theinterests of brevity.

Referring to FIG. 5, there is shown a collecting optical system lens220, a fiber optics collector lens 207 and a fiber optics ball 208 incombination quite similar to their counterparts of lens 20, lens 7 andball 8 of FIG. 1. The output of fiber optics ball 208 is passed througha fiber optics pipe 250 which may include a right angle bend 251, passesthrough another fiber optic ball 252 through a linear portion of fiberoptics pipe 253, then through a third fiber optics ball 254 to a rightangle fiber optics pipe 255 to the camera pick-up tube 201. The angle ofswing of each axis or rotation of the balls 208, 252 and 254 and shownby 0 0 and 0 respectively, which can be for example 45". The ball ineach case swings through an angle of 0/2. This means that the lens cansweep through plus or minus with no rotation of the image or change offocus.

Therefore. while particular embodiments of the subject invention havebeen shown and described herein, they are in the nature of descriptionrather than illustration, and it will occur to those skilled in the artthat various changes, modifications and combinations may be made withinthe provisions of the appended claims without departing from either thespirit or scope of this invention in its broader aspects.

What is claimed as new and desired to be secured by Letters Patent inthe United States is:

l. A fiber optics scan system utilizing fiber optic bundle memberscomprising:

a first spherical fiber optics member, its fibers extending parallel toa central optical axis,

means for supporting said first fiber optics member for universalrotation about its center,

a second fiber optics member having its fibers extending parallel to acentral optical axis and having a concave portion contiguous to andmating with a first portion of said spherical member with the opticalaxes thereof being mutually oriented for image transfer,

optical means to focus a spherical image of an instant portion of alarger scanned field on the surface of said spherical member,

means for supporting said optical means for universal rotation aboutsaid center with the optical axes of said optical means and saidspherical member being mutually oriented for image transfer through thefibers of said spherical member, and

means for coaxially rotating said spherical member and said opticalmeans with said spherical member rotating at one-half the angular rateof said Optical means to scan successive instant portions of saidscanned field.

2. The arrangement set forth in claim 1 wherein a liquid lubricant isprovided between the mating surfaces of said fiber optics members havinga refractive index similar to that of said fiber optics members.

3. The arrangement set forth in claim 2 wherein said optical meansincludes a third fiber optics member having its fibers extendingparallel to said central optical axis and having a concave portioncontiguous to and mating with another portion of said spherical member,said liquid lubricant also lying between the mating surfaces of saidmembers.

4. The arrangement set forth in claim 3 wherein a 20 liquid reservoir isprovided surrounding said spherical member for containing saidlubricant.

5. The arrangement set forth in claim 3 wherein said coaxially rotatingmeans comprises resilient members secured between said spherical andsaid second and third fiber optics members respectively.

6. The arrangement set forth in claim 3 wherein said coaxially rotatingmeans comprises a plurality of springs secured between said sphericaland said second and third fiber optics members respectively.

References Cited UNITED STATES PATENTS 2,093,288 9/1937 Ogloblinsky.2,939,362 6/1960 Cole.

3,05 0,907 8/1962 Hicks et al. 3,221,591 12/1965 Schepler.

JOHN K. CORBIN, Primary Examiner.

